Method and device for generating optical signals

ABSTRACT

The method includes: receiving a first Non Return to Zero (NRZ) data signal and a synchronous clock signal, and performing Return to Zero (RZ) processing to generate a first complementary RZ data signal pair; receiving a second NRZ data signal and a synchronous clock signal, and performing RZ processing to generate a second complementary RZ data signal pair; and modulating the first complementary RZ data signal pair and the second complementary RZ data signal pair on light to generate an RZ-Differential Quadrature Phase Shift Keying (RZ-DQPSK) optical signal. Through the method and device, RZ processing are performed on the NRZ data signals to generate the complementary RZ data signal pairs, and the complementary RZ data signal pairs are modulated on the light, thereby reducing the cost and the insertion loss of the entire device, lowering the requirements for input optical power and reducing the complexity of loop circuit control.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2009/071267, filed on Apr. 15, 2009, which claims priority toChinese Patent Application No. 200810128734.2, filed on Jun. 20, 2008,both of which are hereby incorporated by reference in their entireties.

FIELD OF THE TECHNOLOGY

The present invention relates to the field of communications, and moreparticularly to a method and device for generating optical signals.

BACKGROUND OF THE INVENTION

With the increasing demand for optical network capacity, the servicetransmission rate is developing from 10 Gb/s rate of current networks to40 Gb/s and even 100 Gb/s. In high-speed optical transmission systems,selection of an optical modulation format is critical in the wholesystem. The optical modulation format is directly correlated to theproperties of the optical transmission system such as transmissionperformance, spectral efficiency, nonlinear tolerance, and dispersiontolerance.

As a novel modulation format, a Return to Zero-Differential QuadraturePhase Shift Keying (RZ-DQPSK) modulation format has a narrow spectralwidth, can effectively inhibit nonlinear effects of various opticalfibers and improve the tolerance to chromatic dispersion andpolarization mode dispersion, and becomes an important modulation modefor long-distance high-speed large-capacity optical transmission.

FIG. 1 shows a device for generating RZ-DQPSK optical signals in theprior art. As shown in FIG. 1, an RZ-DQPSK optical signal is generatedthrough two stages of modulators. The first stage is a data modulator,including two differential Mach-Zender Modulators (MZMs) and a ^(ρ)/2phase shifter; and the second stage is a clock modulator. FIG. 2 is aflow chart of generation of an RZ-DQPSK optical signal in the prior art,which includes the following steps. A first MZM is loaded with an NRZsignal 1 to generate a Non Return to Zero-Differential Phase ShiftKeying (NRZ-DPSK) code 1, and similarly, a second MZM generates anNRZ-DPSK code 2. The NRZ-DPSK code 1 and the NRZ-DPSK code 2 passthrough a ^(ρ)/2 phase shifter, and are combined into an NRZ-DQPSKoptical signal. The clock modulator is loaded with a synchronous clocksignal, and generates an NRZ pulse envelope as driven by the clocksignal, and cut the pulse of the NRZ-DQPSK signal to generate anRZ-DQPSK optical signal. Another solution in the prior art is to reversethe order of the first stage modulator and the second stage modulator togenerate an RZ-DQPSK optical signal.

In the implementation of the present invention, the inventor found thatthe prior art has at least the following problems.

In the prior art, the two stages of modulators are used to generate theRZ-DQPSK optical signal, which results in complex structure, high costs,and large volume of the device for generating optical signals.Meanwhile, the clock modulator increases the overall insertion loss(that is, a ratio of the output optical power to the input opticalpower) of the modulators, and in order to maintain the output opticalpower unchanged, the requirements for the input optical power areincreased. The clock modulator needs to control a bias point, whichincreases the complexity of loop circuit control. In addition, the phaseof the clock must be synchronous with that of the data signal, but thesynchronization control method is complex.

SUMMARY OF THE INVENTION

In order to simplify the structure of the device for generating opticalsignals, reduce the costs and the insertion loss of the entire device,lower the requirements for input optical power and reduce the complexityof loop circuit control, the present invention is directed to a methodand device for generating optical signals. The technical solution is asfollows.

A method for generating optical signals is provided, which includes thefollowing steps.

A first NRZ data signal and a synchronous clock signal are received, andRZ processing is performed to generate a first complementary RZ datasignal pair.

A second NRZ data signal and a synchronous clock signal are received,and RZ processing is performed to generate a second complementary RZdata signal pair.

The first complementary RZ data signal pair and the second complementaryRZ data signal pair are modulated on light to generate an RZ-DQPSKoptical signal.

A device for generating optical signals is provided, which includes asignal processing module and a modulator.

The signal processing module is configured to receive a first NRZ datasignal and a synchronous clock signal, and perform RZ processing togenerate a first complementary RZ data signal pair; and receive a secondNRZ data signal and a synchronous clock signal, and perform RZprocessing to generate a second complementary RZ data signal pair.

The modulator is configured to receive input light, the firstcomplementary RZ data signal pair, and the second complementary RZ datasignal pair, and modulate the first complementary RZ data signal pairand the second complementary RZ data signal pair on the light togenerate an RZ-DQPSK optical signal.

The technical solution of the present invention has the followingbeneficial effects.

RZ processing is performed on the NRZ data signals to generate a pair ofcomplementary RZ data signal pairs, and the two RZ data signal pairs aremodulated on light to generate an RZ-DQPSK optical signal without addinga clock modulator to cut the pulse of the NRZ-DQPSK signal to generatethe RZ-DQPSK optical signal, so that the structural complexity and thecost of the device for generating optical signals are reduced, and atthe same time, the insertion loss caused by the clock modulator isreduced, and the requirements for input optical power are lowered. Sinceno clock modulator is added in the present invention, the control of thebias point of the clock modulator is not required, so that thecomplexity of control caused by the clock modulator is reduced.Meanwhile, since no clock synchronization control caused by the clockmodulator is involved, the complexity of synchronization control isreduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a device for generating RZ-DQPSK optical signals in theprior art;

FIG. 2 is a flow chart of generation of an RZ-DQPSK optical signal inthe prior art;

FIG. 3 is a schematic view of generation of an optical signal accordingto a first embodiment of the present invention;

FIG. 4 is a flow chart of a method for generating optical signalsaccording to the first embodiment of the present invention;

FIG. 5 is a schematic flow chart of generation of a complementary RZdata signal pair according to the first embodiment of the presentinvention; and

FIG. 6 is a schematic flow chart of generation of an RZ-DQPSK signalaccording to the first embodiment of the present invention; and

FIG. 7 is a schematic structural view of a device for generating opticalsignals according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

To make the technical solution, objectives and merits of the presentinvention clearer, the embodiments of the present invention is describedin detail with reference to accompanying drawings.

According to the embodiments of the present invention, a first NRZ datasignal and a synchronous clock signal are received, and RZ processing isperformed to generate a first complementary RZ data signal pair; asecond NRZ data signal and a synchronous clock signal are received, andRZ processing is performed to generate a second complementary RZ datasignal pair; and the first complementary RZ data signal pair and thesecond complementary RZ data signal pair are modulated on light togenerate an RZ-DQPSK optical signal.

EMBODIMENT 1

In this embodiment, two differential amplifiers respectively receive anNRZ data signal and a synchronous clock signal, and perform RZprocessing on the two NRZ data signals to generate two RZ data signalpairs, where each pair of RZ data signals contain two complementary RZdata signals. At the same time, the two RZ data signal pairs are loadedonto a modulator to modulate light input into the modulator, so as togenerate an RZ-DQPSK optical signal.

It should be noted that, although in this embodiment, two differentialamplifiers are used to respectively receive an NRZ data signal and asynchronous clock signal and perform RZ processing on the two NRZ datasignals, other manners may also be adopted, for example, two logiccircuit units (for example, a combination of an AND gate and an OR gate)are used to respectively perform RZ processing on the two NRZ datasignals, or an integrated differential amplifier or a logic circuit isused to load a synchronous clock signal for the two NRZ data signals andperform RZ processing. The principle of the logic circuit unit issimilar to that of the differential amplifier, and the principle of thelogic circuit is similar to that of the integrated differentialamplifier, which will not be described in detail in this embodiment.

In this embodiment, taking a schematic view of generation of an opticalsignal shown in FIG. 3 as an example, two differential amplifiers areused to respectively load two synchronous clock signals for two NRZ datasignals, and perform RZ processing. In FIG. 3, a first differentialamplifier, a second differential amplifier, and a modulator areincluded. The modulator includes a first differential MZM, a seconddifferential MZM, a phase shifter, and a combining module.

FIG. 4 shows a method for generating optical signals according to thefirst embodiment of the present invention. As shown in FIG. 4, themethod includes the following steps.

The first differential amplifier receives a first NRZ data signal and afirst synchronous clock signal.

The first NRZ data signal is an electrical signal including “0” and “1”data information. The first synchronous clock signal is an electricalsignal, which is an RZ pulse sequence with a waveform of all “1”s. Thefirst synchronous clock signal is synchronous with the first NRZ datasignal, and the term “synchronous” means that the clock signal and thedata signal have the same frequency and the same initial phase.Specifically, synchronization of the first synchronous clock signal andthe first NRZ data signal may be implemented by performing clock datarecovery (CDR) through an existing phase lock loop (PLL) circuit, and byusing the technique, a clock signal of the same frequency and the samephase can be recovered from the data signal, and thus synchronization ofthe data signal and the clock signal is achieved. It should beunderstood that, the implementation of the synchronization of the datasignal and the clock signal is not limited to the above circuit ortechnique.

The first differential amplifier performs RZ processing on the first NRZdata signal and the first synchronous clock signal to generate a firstcomplementary RZ data signal pair.

Specifically, since the first synchronous clock signal in thisembodiment is an RZ pulse sequence with a waveform of all “1”s, thesynchronous clock signal has the characteristics of RZ. At the sametime, the first NRZ data signal and the first synchronous clock signalare subjected to an operation of an internal circuit of the differentialamplifier, and a pair of complementary RZ data signals are output. Thepair of complementary RZ data signals is an electrical data signalincluding two RZ data signals. The terms “complementary” means that whenthe first RZ data signal is “0”, the second RZ data signal is “1”accordingly; and similarly, when the first RZ data signal is“1”, thesecond RZ data signal is “0” accordingly.

The second differential amplifier receives a second NRZ data signal anda second synchronous clock signal.

The principle of receiving the second NRZ data signal and the secondsynchronous clock signal by the second differential amplifier is similarto that of receiving the first NRZ data signal and the first synchronousclock signal by the first differential amplifier, where the second NRZdata signal and the first NRZ data signal may carry the same datainformation or different data information.

The second synchronous clock signal and the first synchronous clocksignal may be generated by the same clock source or different clocksources. When different clock sources are used, the first synchronousclock signal and the second synchronous clock signal need to besynchronized (that is, the two clock signals have the same frequency andthe same phase), and the synchronization of the signals may be performedby controlling starting points of the clock sources by a logic circuit.

The second differential amplifier performs RZ processing on the secondNRZ data signal and the second synchronous clock signal to generate asecond complementary RZ data signal pair.

The principle of performing RZ processing on the second NRZ data signaland the second synchronous clock signal by the second differentialamplifier to generate the second complementary RZ data signal pair isthe same as that of performing RZ processing on the first NRZ datasignal and the first synchronous clock signal by the first differentialamplifier to generate the first complementary RZ data signal pair, sothe details will not be described herein again.

The first complementary RZ data signal pair and the second complementaryRZ data signal pair are modulated on light by a modulator to generate anRZ-DQPSK optical signal.

The modulator includes a first differential MZM, a second differentialMZM, a ^(ρ)/2 phase shifter, and a combining module. The firstcomplementary RZ data signal pair is loaded onto two arms of the firstdifferential MZM simultaneously. As for a modulation curve in the firstdifferential MZM, the first complementary RZ data signal pair is loadedat the same time. A combined drive voltage is equal to a voltagedifference of the first complementary RZ data signal pair, that is, thesignals are combined into a first electrical RZ driving signal having alevel of “1” and “−1”. The electrical RZ driving signal drives the firstdifferential MZM to modulate one beam of light input into the firstdifferential MZM after being split, so as to generate a first RZ-DPSKdata signal, which is an optical signal. Similarly, the secondcomplementary RZ data signal pair is loaded onto two arms of the seconddifferential MZM, and the other beam of the light after being split ismodulated by the second differential MZM, so as to generate a secondRZ-DPSK data signal. The two beams have the same optical power.

One of the first RZ-DPSK data signal and the second RZ-DPSK data signalis phase-shifted by the ^(ρ)/2 phase shifter, and the phase-shiftedRZ-DPSK data signal and the RZ-DPSK data signal that is notphase-shifted are combined by the combining module to generate anRZ-DQPSK data signal, which is an optical signal.

According to the solution of this embodiment, FIG. 5 provides theprinciple of generation of a complementary RZ data signal pair by takinga specific NRZ data signal as an example. As shown in FIG. 5, the NRZdata signal and the synchronous clock signal are input into thedifferential amplifier simultaneously, and data information carried bythe NRZ data signal is “1 0 1 1”. A complementary RZ data signal pair isgenerated by an internal differential structure of the differentialamplifier. Data information carried by an RZ data signal 1 is the sameas the data information carried by the input NRZ data signal and is “1 01 1”; and the other RZ data signal 2 is complementary to the RZ datasignal 1, and data information carried by the RZ data signal 2 is “0 1 00”. The two complementary RZ data signals are loaded onto two arms ofthe differential MZM simultaneously, and as for a modulation curve inthe differential MZM, it is equivalent to loading a combined RZ drivevoltage, and the waveform of the RZ drive voltage is as the lastwaveform shown in FIG. 5. Data information carried by the RZ drivevoltage is the same as the data information of the initially input NRZdata signal (that is, “1 0 1 1”), but the level of the drive voltage ischanged to “1 −1 1 1”. According to the differential driving principleof MZM, the waveform is formed by phase-reversing the waveform of an RZdata signal carrying the data information complementary to that carriedby the NRZ data signal and then superposing on the waveform of an RZdata signal carrying the same data information as that carried by theNRZ data signal, and thus an electrical RZ driving signal, that is, theRZ drive voltage is generated.

FIG. 6 is a schematic flow chart of generation of an RZ-DQPSK signal. Asshown in FIG. 6, the complementary RZ data signal pair generated in FIG.5 is loaded onto the differential MZM, which is equivalent to that thecombined electrical RZ driving signal modulates the light input into thedifferential MZM, to generate an RZ-DPSK optical data signal; andsimilarly, another RZ-DPSK optical data signal is generated. One RZ-DPSKoptical data signal is phase-shifted by the ^(ρ)/2 phase shifter, andthen the two RZ-DPSK optical data signals are combined to generate anRZ-DQPSK optical data signal.

In this embodiment, RZ processing is performed on the NRZ data signalsto generate a pair of complementary RZ data signal pairs, and the two RZdata signal pairs are modulated on light to generate an RZ-DQPSK opticalsignal without adding a clock modulator to cut the pulse of theNRZ-DQPSK signal to generate the RZ-DQPSK optical signal, so that thestructural complexity and the cost of the device for generating opticalsignals are reduced, and at the same time, the insertion loss caused bythe clock modulator is reduced, and the requirements for input opticalpower are lowered. In the prior art, electrical drive signals are loadedonto a modulation curve by modulators, and all the modulators includingthe clock modulator need to control the bias point, while the control ofthe bias point belongs to phase control, and the clock modulator needsto control the bias point at a correct position, so as to work normally;however, since the bias point may drift, the complexity of control forthe bias point control of the clock modulator is increased. In thisembodiment, since no clock modulator is added, the control of the biaspoint of the clock modulator is not required, so that the complexity ofcontrol caused by the clock modulator is reduced. Meanwhile, in theprior art, the clock modulator serving as the second stage modulatorneeds to synchronize the clock signal with the optical signal output bythe first stage modulator when loading the clock signal, that is, thesynchronization of the clock modulator is synchronizing the opticalsignal; however, compared with the synchronization of the electricalsignal, the method for controlling the synchronization of the opticalsignal is complex. Since no clock modulator is used in this embodiment,no synchronization control of the optical signal is involved, so thatthe complexity of synchronization control is reduced.

EMBODIMENT 2

FIG. 7 shows a device for generating optical signals according to asecond embodiment of the present invention. As shown in FIG. 7, thedevice includes a signal processing module 300 and a modulator 400.

The signal processing module 300 is configured to receive a first NRZdata signal and a synchronous clock signal, perform RZ processing togenerate a first complementary RZ data signal pair, and output the firstcomplementary RZ data signal pair; and receive a second NRZ data signaland a synchronous clock signal, perform RZ processing to generate asecond complementary RZ data signal pair, and output the secondcomplementary RZ data signal pair.

The modulator 400 is configured to receive input light, the firstcomplementary RZ data signal pair, and the second complementary RZ datasignal pair, and modulate the first complementary RZ data signal pairand the second complementary RZ data signal pair on the light togenerate an RZ-DQPSK optical signal.

The signal processing module 300 includes a first differential amplifier300 a, configured to receive the first NRZ data signal and a firstsynchronous clock signal, perform RZ processing to generate the firstcomplementary RZ data signal pair, and output the first complementary RZdata signal pair.

The signal processing module 300 further includes a second differentialamplifier 300 b, configured to receive the second NRZ data signal and asecond synchronous clock signal, perform RZ processing to generate thesecond complementary RZ data signal pair, and output the secondcomplementary RZ data signal pair.

The signal processing module 300 may also include a first logic circuitunit and a second logic circuit unit.

The first logic circuit unit is configured to receive the first NRZ datasignal and a first synchronous clock signal, perform RZ processing togenerate the first complementary RZ data signal pair, and output thefirst complementary RZ data signal pair.

The second logic circuit unit is configured to receive the second NRZdata signal and a second synchronous clock signal, perform RZ processingto generate the second complementary RZ data signal pair, and output thesecond complementary RZ data signal pair.

The modulator 400 includes a light input port 400 a, a firstsub-modulator 400 b, a second sub-modulator 400 c, a phase shifter 400d, and a combining module 400 e.

The light input port 400 a is configured to receive light, and split thelight into two beams.

The light input port 400 a splits the light into two beams, and the twobeams have the same optical power.

The first sub-modulator 400 b is configured to receive one beam from thelight input port 400 a and the first complementary RZ data signal pairoutput by the signal processing module 300, modulate the firstcomplementary RZ data signal pair on the beam to generate a firstRZ-DPSK signal, and output the first RZ-DPSK signal.

The second sub-modulator 400 c is configured to receive the other beamfrom the light input port 400 a and the second complementary RZ datasignal pair output by the signal processing module 300, modulate thesecond complementary RZ data signal pair on the other beam to generate asecond RZ-DPSK signal, and output the second RZ-DPSK signal.

The phase shifter 400 d is configured to perform a ^(ρ)/2-phase shift onthe second RZ-DPSK signal.

The combining module 400 e is configured to receive the first RZ-DPSKsignal output by the first sub-modulator 400 b and the phase-shiftedsecond RZ-DPSK signal output by the phase shifter 400 d, and combine thetwo RZ-DPSK signals to generate an RZ-DQPSK optical signal.

In the implementation of this embodiment, the combining module 400 e islocated in the modulator 400, and achieves the function of combining twosignals into one signal through a medium capable of transmitting light.

The first sub-modulator 400 b and the second sub-modulator 400 c may beimplemented by differential MZMs.

The device for generating optical signals according to this embodimentfurther includes a clock source, configured to generate the firstsynchronous clock signal and the second synchronous clock signal, wherethe first synchronous clock signal is synchronous with the first NRZdata signal, the second synchronous clock signal is synchronous with thesecond NRZ data signal, and the first synchronous clock signal issynchronous with the second synchronous clock signal.

In this embodiment, the first differential amplifier 300 a is used toperform RZ processing on the NRZ data signals to generate the firstcomplementary RZ data signal pair, the second differential amplifier 300b is used to perform RZ processing on the NRZ data signals to generatethe second complementary RZ data signal pair, and the two RZ data signalpairs are modulated on light by the modulator 400 to generate anRZ-DQPSK optical signal without adding a clock modulator to cut thepulse of the NRZ-DQPSK signal to generate the RZ-DQPSK optical signal,so that the structural complexity and the cost of the device forgenerating optical signals are reduced, and at the same time, theinsertion loss caused by the clock modulator is reduced, and therequirements for input optical power are lowered. Since no clockmodulator is added in this embodiment, the control of the bias point ofthe clock modulator is not required, so that the complexity of controlcaused by the clock modulator is reduced. Meanwhile, since no clocksynchronization control caused by the clock modulator is involved, thecomplexity of synchronization control is reduced.

EMBODIMENT 3

In this embodiment, a device for generating optical signals is provided.The difference between this embodiment and the previous embodiment liesin that the signal processing module is an integrated differentialamplifier, and the integrated differential amplifier receives a firstNRZ data signal, a second NRZ data signal, and a synchronous clocksignal simultaneously, where the three signals are synchronous (that is,the three signals have the same frequency and the same initial phase).It should be noted that, the synchronization of the three signals may beimplemented by performing CDR through an existing PLL circuit. The threesignals pass through the integrated differential amplifier, andaccording to the differential principle in the integrated differentialamplifier, a first complementary RZ data signal pair and a secondcomplementary RZ data signal pair are generated simultaneously, that is,one integrated differential amplifier achieves the functions of twodifferential amplifiers in the second embodiment. Then, the firstcomplementary RZ data signal pair and the second complementary RZ datasignal pair are loaded onto two differential MZMs respectively, andmodulated by the differential MZMs, and finally, an RZ-DQPSK opticaldata signal is generated. The principle is similar to that in theprevious embodiment, so the details will not be described herein again.

The signal processing module may also be a logic circuit, and thefunction of the logic circuit is similar to that of the integrateddifferential amplifier, that is, one logic circuit achieves thefunctions of two logic circuit units in the second embodiment, so thedetails will not be described herein again.

The device for generating optical signals according to this embodimentfurther includes a clock source, configured to generate a thirdsynchronous clock signal, where the third synchronous clock signal issynchronous with the first NRZ data signal and the second NRZ datasignal.

Besides the effects of the second embodiment, according to thisembodiment, the integrated differential amplifier performs RZ processingon the two NRZ data signals at the same time, that is, one integrateddifferential amplifier achieves the functions of two differentialamplifiers, so that the structural complexity of the device forgenerating optical signals is significantly reduced.

The above descriptions are merely some exemplary embodiments of thepresent invention, but not intended to limit the scope of the presentinvention. Any modification, equivalent replacement, or improvement madewithout departing from the spirit and principle of the present inventionshould fall within the scope of the present invention.

1. A method for generating optical signals, comprising: receiving afirst Non Return to Zero (NRZ) data signal and a synchronous clocksignal, and performing Return to Zero (RZ) processing to generate afirst complementary RZ data signal pair; receiving a second NRZ datasignal and a synchronous clock signal, and performing RZ processing togenerate a second complementary RZ data signal pair; and modulating thefirst complementary RZ data signal pair and the second complementary RZdata signal pair on light to generate an RZ-Differential QuadraturePhase Shift Keying (RZ-DQPSK) optical signal.
 2. The method forgenerating optical signals according to claim 1, wherein: the receivingthe first NRZ data signal and the synchronous clock signal comprisesreceiving the first NRZ data signal and a first synchronous clocksignal; and the receiving the second NRZ data signal and the synchronousclock signal comprises receiving the second NRZ data signal and a secondsynchronous clock signal.
 3. The method for generating optical signalsaccording to claim 2, wherein the first synchronous clock signal issynchronous with the second synchronous clock signal.
 4. The method forgenerating optical signals according to claim 1, wherein: the receivingthe first NRZ data signal and the synchronous clock signal comprisesreceiving the first NRZ data signal and a third synchronous clocksignal; the receiving the second NRZ data signal and the synchronousclock signal comprises receiving the second NRZ data signal and thethird synchronous clock signal; and wherein the third synchronous clocksignal is synchronous with the first NRZ data signal and the second NRZdata signal.
 5. The method for generating optical signals according toclaim 1, wherein the modulating the first complementary RZ data signalpair and the second complementary RZ data signal pair on the lightcomprises: receiving light, and splitting the light into two beams;modulating the first complementary RZ data signal pair on one beam togenerate a first RZ-Differential Phase Shift Keying (RZ-DPSK) signal;modulating the second complementary RZ data signal pair on the otherbeam to generate a second RZ-DPSK signal; and phase-shifting the firstRZ-DPSK signal or the second RZ-DPSK signal, and combining the twoRZ-DPSK signals to generate an RZ DQPSK optical signal.
 6. A device forgenerating optical signals, comprising: a signal processing module,configured to receive a first Non Return to Zero (NRZ) data signal and asynchronous clock signal, perform Return to Zero (RZ) processing togenerate a first complementary RZ data signal pair, and output the firstcomplementary RZ data signal pair and receive a second NRZ data signaland a synchronous clock signal, perform RZ processing to generate asecond complementary RZ data signal pair, and output the secondcomplementary RZ data signal pair; and a modulator, configured toreceive input light, the first complementary RZ data signal pair, andthe second complementary RZ data signal pair, and modulate the firstcomplementary RZ data signal pair and the second complementary RZ datasignal pair on the light to generate an RZ-Differential Quadrature PhaseShift Keying (RZ-DQPSK) optical signal.
 7. The device for generatingoptical signals according to claim 6, wherein the signal processingmodule comprises: a first differential amplifier, configured to receivethe first NRZ data signal and a first synchronous clock signal, performRZ processing to generate the first complementary RZ data signal pair,and output the first complementary RZ data signal pair; and a seconddifferential amplifier, configured to receive the second NRZ data signaland a second synchronous clock signal, perform RZ processing to generatethe second complementary RZ data signal pair, and output the secondcomplementary RZ data signal pair.
 8. The device for generating opticalsignals according to claim 6, wherein the signal processing modulecomprises: a first logic circuit unit, configured to receive the firstNRZ data signal and a first synchronous clock signal, perform RZprocessing to generate the first complementary RZ data signal pair, andoutput the first complementary RZ data signal pair; and a second logiccircuit unit, configured to receive the second NRZ data signal and asecond synchronous clock signal, perform RZ processing to generate thesecond complementary RZ data signal pair, and output the secondcomplementary RZ data signal pair.
 9. The device for generating opticalsignals according to claim 6, wherein the signal processing modulecomprises an integrated differential amplifier, configured to receivethe first NRZ data signal, the second NRZ data signal, and a thirdsynchronous clock signal, perform RZ processing to generate the firstcomplementary RZ data signal pair and the second complementary RZ datasignal pair, and output the first complementary RZ data signal pair andthe second complementary RZ data signal pair.
 10. The device forgenerating optical signals according to claim 6, wherein the signalprocessing module comprises a logic circuit, configured to receive thefirst NRZ data signal, the second NRZ data signal, and a thirdsynchronous clock signal, perform RZ processing to generate the firstcomplementary RZ data signal pair and the second complementary RZ datasignal pair, and output the first complementary RZ data signal pair andthe second complementary RZ data signal pair.
 11. The device forgenerating optical signals according to claim 6, wherein the modulatorcomprises: a light input port, configured to receive light, and splitthe light into two beams; a first sub-modulator, configured to receiveone beam from the light input port and the first complementary RZ datasignal pair output by the signal processing module, modulate the firstcomplementary RZ data signal pair on the beam to generate a firstRZ-Differential Phase Shift Keying (RZ-DPSK) signal, and output thefirst RZ-DPSK signal; a second sub-modulator, configured to receive theother beam from the light input port and the second complementary RZdata signal pair output by the signal processing module, modulate thesecond complementary RZ data signal pair on the other beam to generate asecond RZ-DPSK signal, and output the second RZ-DPSK signal; a phaseshifter, configured to phase-shift the second RZ-DPSK signal; and acombining module, configured to receive the first RZ-DPSK signal outputby the first sub-modulator and the phase-shifted second RZ-DPSK signaloutput by the phase shifter, and combine the two RZ-DPSK signals togenerate an RZ-DQPSK optical signal.
 12. The device for generatingoptical signals according to claim 6, further comprising a clock source,configured to generate the synchronous clock signal.
 13. The device forgenerating optical signals according to claim 7, further comprising: aclock source, configured to generate the first synchronous clock signaland the second synchronous clock signal, wherein the first synchronousclock signal is synchronous with the first NRZ data signal; the secondsynchronous clock signal is synchronous with the second NRZ data signal;and the first synchronous clock signal is synchronous with the secondsynchronous clock signal.
 14. The device for generating optical signalsaccording to claim 8, further comprising a clock source, configured togenerate the first synchronous clock signal and the second synchronousclock signal, wherein the first synchronous clock signal is synchronouswith the first NRZ data signal, the second synchronous clock signal issynchronous with the second NRZ data signal, and the first synchronousclock signal is synchronous with the second synchronous clock signal.15. The device for generating optical signals according to claim 9,further comprising a clock source, configured to generate the thirdsynchronous clock signal, wherein the third synchronous clock signal issynchronous with the first NRZ data signal and the second NRZ datasignal.
 16. The device for generating optical signals according to claim10, further comprising a clock source, configured to generate the thirdsynchronous clock signal, wherein the third synchronous clock signal issynchronous with the first NRZ data signal and the second NRZ datasignal.